1. Technical Field
A fluid mixer is disclosed wherein the clamping force imposed on the container or containers loaded into the mixer is determined by one of two events that can occur after the upper clamping plate engages the top(s) of the container(s) disposed on the lower clamping plate: (1) if the motor current increases above a predetermined level, the container(s) are automatically determined to be of the non-compressible type, the motor is stopped and the mixing operation can begin; or (2) if the system senses a continued downward travel of the upper plate after initial contact with the container(s) of a predetermined distance, the container(s) is determined to be compressible (e.g. plastic), the motor is stopped and the mixing operation can begin.
2. Description of the Related Art
Many types of fluids need to be mixed or blended into homogenous mixtures in the same containers in which they are sold to a consumer. One example of such in-container mixing results from colorants or pigments being added to base paints at a retail paint store or paint department of a home improvement store. The mixers or mixing machines may operate by vibration, roto-vibration, gyroscopic motion or rotational motion. The forces exerted on the containers during the mixing process are violent.
To ensure that the container or containers stay in position during the violent mixing operation, various clamping mechanisms have been employed. Until recently, the amount of clamping force imposed on a conventional metal cylindrical container (e.g., 1 gal.) or plastic cylindrical container (e.g., 5 gal.) was not crucial as the containers were extremely rugged, and therefore it is difficult to damage a conventional container by over-clamping.
However, paint has become available in rectangular and cubical plastic containers which are not as robust as the conventional cylindrical containers. Further, there is a need to blend or custom mix colors of paint in the new rectangular containers. One rectangular paint container has a handle molded into one corner for the painter's convenience in pouring paint from the container. Such a rectangular paint container has a rectangular or square footprint or cross section. Another new type of container includes rectangular trays or trough-like buckets sized to receive a paint roller. Some of the rectangular trays or troughs may be pre-equipped with a screen or insert for engaging the roller. Smaller plastic cylindrical containers are also being used instead of the traditional metal cylindrical containers.
The new types of containers are fabricated from plastic and are less robust than the conventional counterparts. Hence, an automatic clamping mechanism of a prior mixing machine is capable of crushing most, if not all, of the new types of containers. To avoid the problem of containers being crushed by the mixing machines and the spillage of paint, new and improved clamping mechanisms and automated clamping mechanisms are needed. Further, such clamping mechanisms must be versatile and capable of use on the various types of containers in the marketplace, both old and new.